1. Field of the Invention
The present invention relates to a method of reducing microloading effect, and more particularly, to a method of reducing microloading effect in a dry etching process.
2. Description of the Prior Art
Electronic devices, such as integrated circuits, are formed by many processes such as deposition, oxidation and etching. In a typical etching process, a patterned mask is formed on the substrate by a conventional lithographic process, and thereafter, exposed portions of the substrate are etched away with energized gases.
An ideal etching process must transfer the pattern on a mask layer to an underlying layer accurately, and also stop at a predetermined depth. However, since the etching process removes a target material both chemically and physically, the etching process is very sensitive to a lot of environmental parameters. One of the most challenging factors in traditional etching control is the microloading effect. Generally speaking, a semiconductor substrate subjected to an etching process is to define a pattern with a plurality of regions. The regions may be distributed with a high density of features and relatively few and isolated features.
Under the chemical and physical reacting mechanism of the etching process, the characteristics of etching are different under the variations of pattern size and density. Because of the microloading effect, different pattern regions are etched to different depths.